Hdd capacity problem

hey guys,
About a year ago I installed a second harddrive(80gb) as a slave on my ancient pentium 4 pc. Bios only identified it as 33.8gb and windows saw it as 31.5gb. I decided not to mess with it and just use it as it is. Now I need more hd space. Do you think the harddrive itself is defective or is it a problem with the bios? I checked the jumpers, they’re not set to a certain capcity they’re just set to slave. I don’t think its bios because my primary is 40gb.
any thoughts?